Recently, a light emitting diode (LED) is spotlighted as a light emitting device. Since the LED can convert electric energy into light energy with high efficiency and long life span of about 5 years or more, the LED can remarkably reduce the energy consumption and repair and maintenance cost. In this regard, the LED is spotlighted in the next-generation lighting field.
Such an LED is prepared as a light emitting semiconductor layer including a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer, in which the active layer generates light according to current applied thereto through the first and second conductive semiconductor layers.
Meanwhile, in the LED, since the second conductive semiconductor layer has relatively high sheet resistance due to low carrier concentration and mobility, a transparent current spreading layer is required to form an ohmic contact interface with respect to a top surface of the second conductive semiconductor layer.
When the transparent current spreading layer including ITO or ZnO is formed on the second conductive semiconductor layer to form an ohmic contact interface, the transparent current spreading layer may form a schottky contact interface instead of the ohmic contact interface due to subsequent processes such as deposition and annealing processes.
In order to improve light extraction efficiency of the LED, researches and studies for forming a light extracting structure having a concave-convex pattern on the surface of the current spreading layer have been carried out. However, when the light extracting structure is formed on the current spreading layer directly provided on the second conductive semiconductor layer, the LED is electrically damaged, so that a driving voltage and a leakage current may be increased.